- If definition of infection is not fulfilled: infection defined as Culture positive: ≥ 3 positive intraoperative cultures (tissue biopsies a.m. Kamme-Lindberg) Culture negative: < 3 positive intraoperative cultures (tissue biopsies a.m. Kamme-Lindberg) + Chronic fistula with history of previous or existing secretion or Positive cultures in pre-operatively joint fluid aspiration with other clinical signs of infection or Visual pus or purulent fluid during exchange procedure with clinical signs of infection